我已经建立了一个应用程序使用Socket.io和安卓网络发现。当服务器启动，android设备解析服务时，我尝试创建一个套接字，但它从未在第一次尝试中工作。我必须杀死这个应用程序并重新启动它，然后它就可以正常工作了。服务器正在接入点上运行。连接到网络是好的，但我不能平服务器。但是正如前面提到的，如果我杀死这个应用程序并再次运行它，它就会运行得很好。

Eidt 2

经过进一步的调试，我将崩溃的范围缩小到应用程序设置wifi连接的任何时候。ssid和密码是从qrcode获得的，应用程序设置wifi连接。

读取qr码数据

        @Override
        public void receiveDetections(Detector.Detections<Barcode> detections) {
            final SparseArray<Barcode> barCodes = detections.getDetectedItems();
            if (!receivedDetection) {
                if (barCodes.size() != 0) {
                    Log.i(TAG, "received a Barcode");
                    receivedDetection = true;
                    Gson g = new Gson();
                    try {
                        barCodeData = g.fromJson(barCodes.valueAt(0).rawValue, AccessPointCredentials.class);
                    } catch (Exception e) {
                        barCodeData = new AccessPointCredentials();
                        barCodeData.setSsid(barCodes.valueAt(0).rawValue);
                        barCodeData.setPass(null);
                        e.printStackTrace();
                    connectToWifi(barCodeData);
        }

connectToWifi()

private void connectToWifi(final AccessPointCredentials credentials) {
    new AsyncTask<Object, Object, Object>() {
        @Override
        protected Object doInBackground(Object... objects) {
            WifiManager wifiManager = (WifiManager) mActivity.getSystemService(Context.WIFI_SERVICE);
            wifiManager.setWifiEnabled(true);
            int netId;
            try {
                Thread.sleep(100);
            } catch (InterruptedException ie) {
                ie.printStackTrace();
            for (WifiConfiguration tmp : wifiManager.getConfiguredNetworks()) {
                if (tmp.SSID.equals("\"" + credentials.getSsid() + "\"")) {
                    netId = tmp.networkId;
                    boolean enabled = wifiManager.enableNetwork(netId, true);
                    Log.i(TAG, "doInBackground: Enabled? " + enabled);
                    mActivity.runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            mActivity.onBackPressed();
                    return null;
            final String[] apSettings = {credentials.getSsid(), credentials.getPass()};
            final WifiConnect WifiTask = new WifiConnect(mActivity);
            mActivity.runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    WifiTask.execute(apSettings);
            this.cancel(true);
            return null;
        @TargetApi(23)
        @Override
        protected void onPostExecute(Object aVoid) {
            super.onPostExecute(aVoid);
            if (Build.VERSION.RELEASE.equalsIgnoreCase("6.0")) {
                if (!Settings.System.canWrite(mActivity)) {
                    Intent goToSettings = new Intent(Settings.ACTION_MANAGE_WRITE_SETTINGS);
                    goToSettings.setData(Uri.parse("package:" + mActivity.getPackageName()));
                    mActivity.startActivity(goToSettings);
                } else {
                    bindToNetwork();
            } else {
                bindToNetwork();
    }.execute();
}

bindToNetwork()

private void bindToNetwork() {
    final ConnectivityManager connectivityManager = (ConnectivityManager) mActivity.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkRequest.Builder builder;
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
        builder = new NetworkRequest.Builder();
        //set the transport type do WIFI
        builder.addTransportType(NetworkCapabilities.TRANSPORT_WIFI);
        connectivityManager.requestNetwork(builder.build(), new ConnectivityManager.NetworkCallback() {
            @Override
            public void onAvailable(Network network) {
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                    connectivityManager.bindProcessToNetwork(network);
                } else {
                    //This method was deprecated in API level 23
                    ConnectivityManager.setProcessDefaultNetwork(network);
                try {
                    //do a callback or something else to alert your code that it's ok to send the message through socket now
                } catch (Exception e) {
                    e.printStackTrace();
                connectivityManager.unregisterNetworkCallback(this);
}

编辑

布尔方法isServerReachable()控制异常

java.net.SocketException: socket failed: ENONET (Machine is not on the network)

public boolean isServerReachable(){
        boolean isReachable;
        try {
            isReachable = InetAddress.getByName(mService.getHost().getHostAddress()).isReachable(5000);
        } catch (Exception e) {
            e.printStackTrace();
            isReachable = false;
        Log.i(TAG, "onServiceResolved: Server reachable? " + String.valueOf(isReachable));
        Log.i(TAG, "onServiceResolved: Is Network online? " + String.valueOf(isNetworkOnline()));